It is known to use check valves to allow fluid flow in one direction, and to prevent flow in the opposite direction. Check valves are widely used in a wide variety of applications, for example in air conditioning systems, for example in aircraft air conditioning systems.
Check valves commonly include a pair of flapper (or valve) elements disposed over a pair of openings in a valve housing. The flapper elements are hingedly supported on a shaft (or ‘hinge-pin’) mounted to the valve housing for rotation between a closed position in which they lie across and close the opening, preventing fluid flow through the opening in one direction and an open position in which, under the pressure of a fluid (gas or liquid) on one side of the check valve, the flapper elements rotate from their closed positions so as to allow the fluid to flow through the valve in the opposite direction.
In known check valve arrangements, a stop is typically provided to limit the rotational movement of the flapper elements as they open. In some arrangements, the stop comprises a stop pin which is mounted to mounting posts arranged on opposed sides of the valve housing opening. The stop pin is spaced from the opening such that when the flappers open, they engage the stop pin.
The flapper elements of such prior art flapper valves typically do not reach the fully open position, and thus the stop pin, simultaneously. This results in a slight delay between impacts against the stop pin, which may result in uneven stress distribution within various components of the check valve, and as a consequence, damage the valve. This may require the components within the check valve to be relatively heavy in order to withstand the impact force of the flapper elements and to avoid the costly and time consuming process of replacing damaged parts. Additionally, uneven pressure distribution across the valve may result in only one of the flapper elements opening, or partially opening, which may diminish valve performance and/or efficiency during operation.
In order to mitigate the aforementioned problem of poor valve efficiencies and unbalanced stress distribution within the check valve, typical prior check valves require the use of power actuation systems to control the flapper elements during operation. Not only does this dramatically increase the complexity and cost of the valve, but also further increases the weight of the check valve, which may have implications in aircraft applications, for example.